Don't forget the fantastic resynthesizer plug-in as part of the tool
chain for creating tilable plug-ins. It is certainly usually much
better than any alpha-blending. See:
http://www.logarithmic.net/pfh/resynthesizer
Regards,
Dov
On 12/29/05, Leon Brooks <leon-gimp@xxxxxxxxxxxxxxxxxxx> wrote:
> On Thursday 29 December 2005 07:20, Carol Spears wrote:
> > the one other thing that would make them useful as patterns is if
> > they can be made tileable. there is at least one plug-in that
> > does this.
>
> OK... having a stab at doing this "manually" for one herringbone pattern
> of brick pavers now, and it ain't as easy as it looks. (-:
>
> This would be a really handy thing to have a dedicated tool (or at least
> plugin) to do. The following comments apply to real-world objects being
> converted to patterns; they may not apply to computer-generated
> patterns.
>
> Each potential tiled texture will probably need some fisheye correction,
> which Dave Hodson's "Telephoto" plugin does reasonably well -- thanks,
> Joao, for reminding me that the plugin existed. This is made a little
> easier by lining image features up against guides, but it's still very
> much trial-and-error. Being able to do it on the main image in real-ish
> time would help a lot.
>
> Many of them will also require "keystone" correction to make them square
> (or at least symmetrical across the X and Y axes). Those which require
> both would be a lot easier to deal with if both this and the fisheye
> correction could be done interactively, realtime(ish) and full-scale on
> a single set of sliders.
>
> Next, we need to isolate (crop to) a section of the subject which is
> suitable for one of the algorithms below. Interactivity would help this
> a lot as well, see discussion for each.
>
> Having made the subject basically rectangular, the next step is to make
> it repeatable. There are two techniques that I've looked at so far.
>
> One consists of replicating the original rectangle in each direction,
> flipping the image over its edge to achieve an image twice as large in
> each direction but which matches exactly along the edges.
>
> This does not work well for asymmetrical subjects, such as those
> containing text or lit predominantly from one side.
>
> Being able to tweak the corrections and cropping on the fly and have it
> displayed as an "endless" pattern would make achieving near-perfect
> results considerably easier.
>
> Storing a single copy of the basic pattern rather than a fourfold-larger
> copy woulod be good, but would require the addition of a different
> tiling mode rather than simple repetition, call it "flip-tiling" if it
> doesn't already have a name.
>
> The other method consists of overlapping the original image with itself
> and alpha-blending the edges of each copy to smooth over differences
> between each edge of the image. This does not work very well if the
> subject is not consistent from edge to edge, but does handle
> asymmetries such as sunlight coming from one side reasonably well.
>
> There is already a plugin to do something like this, but it is *very*
> clumsy and only works acceptably with very complicated, fine-grained
> subjects, or with very near-featureless subjects. Even then, there is
> rectangular meta-pattern visible at larger scales because of the
> unsubtle blending at the edges of the image.
>
> Real-time interactivity would greatly help this mode as well.
>
> It would also benefit from being able to do "gradiented" corrections of
> at least brightness across the subject, possibly automatically or
> semi-automatically by selecting tiles along each edge and adjusting the
> intensity gradient so that they are equal, then another pass to smooth
> the gradient.
>
> Another pair of useful features would be the ability to draw the
> alpha-blending border on each edge of the image freehand and/or with
> beziers, and to adjust the slope (or possibly even curve) of the
> blending. This would allow the operator to better duck around
> anomalies.
>
> A final useful feature would be the ability to arbitrarily deform areas
> of the subject, PowerGoo(tm)-style, in order to better match up the
> edges of random/chaotic patterns like waves or gravel.
>
> Cheers; Leon
>
> --
> http://cyberknights.com.au/ Modern tools; traditional dedication
> http://plug.linux.org.au/ Member, Perth Linux User Group
> http://slpwa.asn.au/ Member, Linux Professionals WA
> http://osia.net.au/ Member, Open Source Industry Australia
> http://linux.org.au/ Member, Linux Australia
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